1. Field of the Invention
The present invention relates to a method and apparatus for teaching robot operations, particularly to an operation teaching method and apparatus in which camera images are used to remotely teach robot tool trajectories.
2. Description of the Prior Art
Methods of providing trajectories for arms of robots engaged in assembly or machine operations include (i) the direct teaching method that uses a teaching box or the like to record locations through which the robot has passed and operates the robot in that order, and (ii) the program method that uses input of numerical data and formulas relating to location and attitude in the workspace.
Direct teaching has the following drawbacks.
(1) With a teaching box it is difficult to teach locations and orientations with high accuracy.
(2) In the case of remote operations, because there is a loss of depth information when only camera images are used, it is difficult to remotely teach robot spatial locations and orientations.
(3) Since each recorded location and orientation is provided separately, it is difficult to satisfy specific spatial relationships, such as, for example, a constraint that a tool is always in the same inclined plane.
Program-based teaching has the following drawbacks.
(4) It is necessary to know beforehand the location and geometry of objects and obstacles in the workspace coordinate system.
(5) The operator cannot intuitively understand teaching based on numerical values and formulas.
To resolve the above problems, the present inventor proposed in JP-A 2001-60108 a method of remotely teaching robot tool trajectories in which the teacher/operator uses image information of the workspace obtained by a camera or cameras to prepare simple, three-dimensional geometric elements corresponding, directly or indirectly, to the actual space, to enable the target task to be carried out readily and safely. In accordance with this method, camera images obtained from a three-dimensional image measuring system are shown on a display which the operator views as he uses an input device to define simple geometric elements based on the three-dimensional information. In this way, the frames necessary for defining the task trajectories of a work robot are set. The term xe2x80x9cframexe2x80x9d is used as a close synonym for xe2x80x9ccoordinate systemxe2x80x9d to represent a 3-D position and orientation hereinafter. A frame has six degrees of freedom in space. Using the measuring system in conjunction with a drive system, such as robot arms, for changing the location and orientation of the measuring system made it possible to teach trajectories with good accuracy over the entire workspace region.
However, a premise of the above method was that the trajectories and the geometric elements comprising the trajectories were all to be defined online. Though some elements may need to be defined indirectly from the complex relationships among geometric elements, this defining had to be carried out on a task by task basis. This meant that even when it was desired to carry out teaching for a similar task, it was necessary to individually prepare each geometric element starting from the beginning. Moreover, the more complex the task trajectories become, the more necessary it is for the teacher to have an advanced knowledge of geometry and a deep understanding of the task structure, which limits the number of teachers capable of doing the teaching involved.
To resolve the above drawbacks, an object of the present invention is to provide a robot operation teaching method and apparatus that makes it possible to speedily and easily teach complex trajectories that vary depending on situations, utilizing an interface apparatus having two-dimensional interface functions.
To attain the above object, the present invention provides a robot operation teaching method comprising: using a three-dimensional measuring system capable of measuring spatial coordinates corresponding to points designated on camera images, a display able to display an actual space image obtained by a camera or cameras with an overlay of a geometric model image corresponding to the actual space image, and a pointing device having at least two degrees of freedom to enable all operator to prepare in a modal space simple geometric elements corresponding to the actual space image, thereby defining work trajectories; wherein by using parametric modelling to pre-define geometric elements, such as trajectories, geometric elements, such as trajectories, adapted for individual situations are produced by modifying a portion of geometric element assignments and parameters associated with a definition.
To attain the above object, the present invention also provides a robot operation teaching apparatus that comprises: a three-dimensional measuring system capable of measuring spatial coordinates corresponding to points designated on camera images; a display that displays an actual space image obtained by a camera or cameras overlaid by a geometric model image of geometric elements corresponding to the actual space image; a pointing device for selecting a location; and means for using parametric modelling to pre-define the geometric elements; the apparatus being able to produce geometric elements adapted for each situation by modification of a portion of geometric element assignments and parameters associated with a definition.
As described above, in the present invention, parametric modelling is used to pre-define trajectories in a form that can describe the spatial constraints between geometric elements determined based on task requirements. As a result, at the actual teaching stage, a required trajectory can be generated by just selecting a trajectory from a menu and teaching the minimum amount of information needed for defining that trajectory. Thus, the operator is able to perform the teaching quickly with less fatigue, without having to take into account details about depth.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and following detailed description of the invention.